Note: Descriptions are shown in the official language in which they were submitted.
WO 2022/235189
PCT/SE2022/050429
1
BIOBASED BINDER COMPOSITIONS FOR AIRLAID NONWOVEN MATERIALS
Technical field
[0001] The present invention relates to biobased binder compositions which are
environmentally benign, renewable, compostable and/or biodegradable. The
biobased compositions comprise chitosan, an acid and a plasticizer. The
invention
further relates to a method of treating an airlaid nonwoven with a biobased
binder
composition according to the present invention.
[0002] The compositions according to the present invention are suitable as a
binder for airlaid nonwoven materials. The treatment of airlaid nonwoven
materials
with a binder composition according to the present invention, provides airlaid
nonwoven materials which exhibit higher elongation, i.e. elongation at break,
and
strength compared to airlaid nonwoven materials treated with previously
available
biobased binders.
Background art
[0003] Airlaid nonwovens are traditionally used in the manufacturing of
disposable diapers, feminine hygiene articles, industrial wipes, wet wipes,
napkins,
table cloths and other products requiring high softness. They are usually
characterized by their bulkiness, softness and high water absorption.
[0004]
In the airlaid process, a continuous web of fibres is formed using air as
medium. Generally, fibres are dispersed in an air stream and deposited on for
instance a moving wire. The resulting deposit is then compressed, for instance
by
pressure or vacuum. However, the material is at this stage totally unbonded
since
it cannot build up an internal strength as for example wetlaid nonwoven or
paper
can due to the hydrogen bonds formed in a wet process.
[0005] In order to achieve bonding or other mechanical improvements in airlaid
nonwovens, a binder is usually added and may be introduced at different stages
in
the manufacturing process depending on the type of binder used. Traditionally,
both liquid binders, slurries, suspensions, foams or powder binders have been
used. The most common bonding technique is the addition of a liquid binder,
such
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
2
as latex, added to the sides of the formed web and subsequentially cured.
Another
bonding alternative is thermal bonding, where synthetic fibres are added to
the
fiber air-dispersion and the resulting nonwoven material is heated resulting
in
bonding between the synthetic fibres.
[0006] Elongation is a key requirement for airlaid nonwoven
materials. If too stiff,
i.e. not flexible with a soft hand feel, the airlaid nonwoven will be
perceived as
unpleasant to the user. Moreover, if the airlaid nonwoven material is not
sufficiently strong and flexible, the material might break apart when used. To
combine strength, soft hand feel and flexibility is thus of crucial importance
when
developing airlaid nonwovens. In addition, the production and processing of
the
material require high elongation and strength.
[0007] In an attempt to reduce the usage of synthetic binders,
i.e. plastic
binders, attention has been drawn to biobased polymers that can substitute the
synthetic polymers used for airlaid nonwovens. Nevertheless, none of the
alternatives so far can achieve an airlaid nonwoven article with sufficiently
high
elongation which is a crucial parameter for such a product.
[0008] Previous attempts have been made to reduce or eliminate the usage of
synthetic binders in nonwovens, such as in W02020068151A1 . However, the
article disclosed in W02020068151 Al still comprises synthetic fibres and/or
wet
strength agents.
[0009] The use of chitosan as a binder component in nonwoven materials has
been examined before, such as in W02012015863 Al. However, as clearly stated
in W02012015863 Al, chitosan as the sole binder is not able to provide
sufficiently good levels of mechanical properties such as for instance tensile
strength. Therefore, a synthetic component, i.e. vinyl acetate ethylene, is
provided
in order to improve these properties as well as strength and elongation
properties.
[0010] Bio-based polyelectrolyte complexes (PEC) have also been studied as
an environmentally friendly binder alternative for materials such as fiber
based
materials, textiles, woven and nonwoven. PECs are association complexes formed
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
3
between oppositely charged polycations and polyanions, formed due to
electrostatic interaction between the oppositely charged polyions. Such a
binder is
for instance described in WO 2018 038671 Al. However, an airlaid nonwoven
treated with a P EC binder composition will only show an elongation of around
3%,
which as previously described is not sufficiently high for an airlaid nonwoven
article. An elongation of around 6 ¨ 9 % is normally required.
[0011] There is thus still a need for a biobased binder for airlaid nonwovens,
providing strength and most importantly elongation properties comparable to
that
of conventional synthetical binders used for airlaid nonwovens.
Summary of invention
[0012] An object of the present invention is to provide a biobased binder
composition suitable as a binder for an airlaid nonwoven material.
[0013] A further object of the invention is to provide a biobased binder
composition which gives sufficiently high elongation to a treated airlaid
nonwoven
material.
[0014] A further object of the invention is to provide a biobased binder
composition that is environmentally friendly, renewable, compostable and/or
biodegradable.
[0015] A further object of the invention is to provide an airlaid nonwoven
which
exhibits strength and sufficiently good elongation, preferably an elongation
of at
least 4 %.
[0016] Any combination of the above objects is also possible.
[0017] In one general aspect, the invention relates to an
aqueous biobased
binder composition for an airlaid nonwoven material, said composition
comprising
an acid, a plasticizer and a cationic polyelectrolyte comprising chitosan, and
wherein;
- the chitosan has a degree of deacetylation of 66 ¨ 100%, and wherein the
composition comprises 0.005 ¨ 20 wt% of chitosan,
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
4
- the acid in the aqueous binder composition is a Bronsted acid and/or a
Lewis
acid, wherein the Bronsted acid is selected from any organic and/or inorganic
acids, wherein the Lewis acid is selected from any cationic mono- or
multivalent
atom, and wherein the aqueous binder composition comprises preferably 0.01 ¨
30 wt% of acid,
- the aqueous binder composition comprises at least 15 wt% of plasticizer,
preferably at least 20 wt% of plasticizer,
- the pH of the aqueous binder composition is less than 7,
and wherein the cationic polyelectrolyte is not in a complex with an anionic
polyelectrolyte.
[0018] By an aqueous biobased binder composition according to the present
invention, a binder for an airlaid nonwoven material comprising a high amount,
or
completely made of, renewable materials is achieved. Furthermore, it has
surprisingly been found that an aqueous binder composition according to the
present invention is able to better act as a binder in an airlaid nonwoven
material,
thus resulting in a material exhibiting both sufficiently high strength and
elongation
compared to conventional synthetic binders used by the industry. Chitosan,
compared to other cationic polyelectrolytes, imparts higher tensile index to a
material treated with the binder composition. Preferably, the binder
composition
comprises at least 50 wt% of biobased, i.e. of natural origin, components,
more
preferably at least 60 wt%, more preferably at least 70 wt%, even more
preferably
at least 80 wt% and most preferably at least 90 wt%.
[0019] It has been found that in a binder composition according to the present
invention, a cationic polyelectrolyte comprising chitosan without the presence
of an
anionic polyelectrolyte counter ion in the composition is able to better
spread
within the airlaid nonwoven material, thus resulting in a more homogenous
distribution. Without being bound by theory, it is believed that the lack of
an
electrostatic interaction between the cationic polyelectrolyte and an anionic
polyelectrolyte, results in a cationic polyelectrolyte in a more expanded
shape. If
the cationic polyelectrolyte was to interact with an anionic counter
component, the
resulting polyelectrolyte complex would exhibit a more coiled structure. By
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
achieving a more expanded shape, it is believed that the cationic
polyelectrolyte is
able to better spread within the airlaid nonwoven structure. This results in a
stronger and more flexible airlaid nonwoven material, compared to if a PEC
binder
composition was used, as the chitosan will act as a binding component linking
with
itself as well as with fibres within the airlaid nonwoven material. The
synergistic
effect between the cationic polyelectrolyte comprising chitosan and the
plasticizer
results in a composition suitable as a binder for airlaid nonwovens that is
able to
achieve both strength as well as elongation of a treated material comparable
to
conventional synthetic binders used.
[0020] It is important that the pH is below 7 in the aqueous
binder composition,
as an acidic environment is needed for the chitosan to be in its cationic
form.
Preferably, the pH of the composition is lower than 6.5, preferably the pH of
the
composition is between 1.8 ¨ 5.
[0021] In one aspect, the aqueous binder composition may further comprise a
solvent selected from distilled water, tap water and deionized water.
[0022] In one aspect, the aqueous binder composition comprises chitosan as
cationic polyelectrolyte, lactic acid as acid, and at least one of sorbitol,
hydrolysed
starch, xylitol and maltitol as plasticizer. Preferably, the plasticizer
comprises
hydrolysed starch.
[0023] The amount of each of the components of the aqueous biobased binder
composition depends on the intended use of the composition and the required
properties necessary for that use, such as for instance strength, softness
and/or
elongation.
[0024] In one aspect, the aqueous binder composition may further
comprise at
least 22 wt% of plasticizer, preferably at least 24 wt%, even more preferably
at
least 25 wt%. In one aspect, the composition comprises 20 - 30 wt% of
plasticizer.
[0025] In one aspect, the cationic polyelectrolyte in the aqueous
binder
composition consists of chitosan.
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
6
[0026] In one aspect, the aqueous binder composition does not
contain an
anionic polyelectrolyte. If a substantial amount of an anionic polyelectrolyte
would
be present in the composition, the cationic and anionic polyelectrolyte would
form
a polyelectrolyte complex (PEC), resulting in an impaired functionality of the
binder
composition as previously described.
[0027] In one aspect, the aqueous binder composition comprises 0.005 ¨ 15
wt% of chitosan, preferably 0.005 ¨ 10 wt%, and even more preferably 0.005 ¨ 5
wt% of chitosan. In one aspect, the composition comprises 0.5 ¨ 3 wt% of
chitosan, even more preferably between 1.5 ¨ 2.5 wt%. The wt% of chitosan is
optimized based on the desired viscosity. Preferably, the composition
comprises
about 2 wt% chitosan. In one aspect, the composition comprises 2.1 wt% of
chitosan.
[0028] In one aspect, the plasticizer is a polyol, preferably the
polyol is selected
from one or more of glycerol, mannitol, maltitol, xylitol and, sorbitol and
saccharides selected from glucose, mannose, fructose, sucrose, sucralose,
sucrose esters, cyclodextrin, hydrolysed starch, dextrin and similar. In one
aspect,
the plasticizer is preferably sorbitol.
[0029] In the context of the plasticizer, hydrolysed starch is a
product from
chemical or enzymatic treatment of starch from various natural sources. The
hydrolysed starch can be hydrogenated and comprise a mixture of polyols,
suitable brands for the present invention can be those with CAS No. 68425-17-2
and/or as No. 1259528-21-6 or the similar.
[0030] In one aspect, the acid is selected from one or more of acetic acid,
acetylsalicylic acid, adipic acid, benzenesulfonic acid, camphorsulfonic acid,
citric
acid, citric acid monohydrate, dihydroxy fumaric acid, formic acid, glycolic
acid,
glyoxylic acid, hydrochloric acid, lactic acid, malic acid, malonic acid,
maleic acid,
mandelic acid, oxalic acid, para-toluenesulfonic acid, phtalic acid, pyruvic
acid,
salicylic acid, sulfuric acid, tartaric acid and succinic acid, preferably
lactic acid.
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
7
[0031] In one aspect, the aqueous binder composition further comprises at
least
one or more of an additive selected from defoamer, foaming agent, wetting
agent,
coalescent agent, catalyst, surfactant, emulsifier, preservative, rheology
modifiers,
fillers, nonionic polymers, dye and pigment, wherein the concentration of the
additive is 0-50 wt% by weight more preferably 0-30% by weight of the total
weight
of the composition. Said additives are selected depending on application
method
and expected final material properties.
[0032] The catalyst can be chosen from Lewis bases and acids, such as clays,
colloidal or noncolloidal silica, dialdehydes, organic amines, organic amides,
quaternary amines, metal oxides, metal sulphates, metal chlorides, urea
sulphates, urea chlorides and catalysts based on silicates.
[0033] The preservative can be selected from one or more of fungicide,
bactericide, pharmaceutical preservative, cosmetic preservative and food
preservatives. The inclusion of a preservative helps to inhibit the growth of
mold in
the binder composition. Moreover, it was discovered that binder compositions
without preservative become more yellow/brown than a binder composition
comprising a preservative. Even if performance is the same between the more
yellow and less yellow composition, the yellow colour is transferred to
material and
causes yellowing which is unwanted.
[0034] The filler may be selected from one or more of gum arabic, konjac
glucomannan, organic fillers such as wood flour, starch soy flour, olive seed
flour,
cork flour, corn cobs, rice brain husks, and inorganic fillers such as calcium
carbonate, glass fibre, kaolin, talc and mice and other fillers known to the
skilled
person.
[0035] In one aspect, the aqueous binder composition comprises 1 ¨ 2.5 wt% of
chitosan, 20 ¨ 40 wt% of plasticizer, 0.05 ¨ 3 wt% of acid and optionally
0.05¨ 10
wt% of at least one or more of an additive selected from defoamer, foaming
agent,
wetting agent, coalescent agent, catalyst, surfactant, emulsifier,
conservative,
cross-linker, rheology modifiers, fillers, nonionic polymers, dye and pigment.
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
8
[0036] In another general aspect, the present invention is directed to a
method
of treating an airlaid nonwoven material with a biobased binder composition,
wherein the method comprises the steps of:
a) providing a binder composition comprising an acid, a plasticizer and a
cationic polyelectrolyte comprising chitosan, wherein the chitosan has a
degree of
deacetylation of 66 ¨ 100%, the acid in the binder composition is a Bronsted
acid
and/or a Lewis acid, wherein the Bronsted acid is selected from any organic
and/or inorganic acids, wherein the Lewis acid is selected from any cationic
mono-
or multivalent atom;
b) optionally, diluting the binder composition to an aqueous binder
composition
according to any one of the previous aspects;
c) applying the composition of step a) or b) to an airlaid nonwoven by
applying
the binder composition on a formed airlaid nonwoven web;
d) optionally curing the treated airlaid nonwoven material, preferably wherein
the
curing is performed at 20 to 200 degrees C.
[0037] In one aspect, the binder composition provided in step a) is an aqueous
binder composition according to any of the previous aspects. In one aspect,
the
aqueous binder composition provided in step a) comprises an acid, a
plasticizer
and a cationic polyelectrolyte comprising chitosan, and wherein;
- the chitosan has a degree of deacetylation of 66 ¨ 100% and wherein the
aqueous binder composition comprises 0.005 ¨ 20 wt% of chitosan;
- the acid in the aqueous binder composition is a Bronsted acid and/or a
Lewis
acid, wherein the Bronsted acid is selected from any organic and/or inorganic
acids, wherein the Lewis acid is selected from any cationic mono- or
multivalent
atom, and wherein the aqueous binder composition comprises preferably 0.01 ¨
30 wt% of acid;
- the aqueous binder composition comprises at least 15 wt% of plasticizer,
preferably at least 20 wt% of plasticizer;
- the pH of the binder composition is less than 7,
and wherein the cationic polyelectrolyte is not in a complex with an anionic
polyelectrolyte.
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
9
[0038] In one aspect of the invention, the binder composition in
step b) is diluted
to an aqueous binder composition comprising 1 ¨ 2.5 wt% of chitosan, 20 ¨40
wt% of plasticizer, 0.05 ¨ 3 wt% of acid and optionally 0.05 ¨ 10 wt% of at
least
one or more of an additive selected from defoamer, foaming agent, wetting
agent,
coalescent agent, catalyst, surfactant, emulsifier, conservative, cross-
linker,
rheology modifiers, fillers, nonionic polymers, dye and pigment.
[0039] By using a method according to the present invention, an airlaid
nonwoven material is achieved exhibiting improved strength and elongation
properties comparable to airlaid nonwovens bonded with conventional binders.
This enables the substitution of conventional binders with a more
environmentally
friendly alternative, without impairing the mechanical properties of the
airlaid
nonwoven material.
[0040] In one aspect, the method results in higher elongation of the treated
airlaid nonwoven, preferably the method results in an elongation of at least 4
%,
preferably at least 6%. As used herein, elongation means the total elongation
at
break measured according to standard Edana 20.2-89.
[0041] In one aspect, the curing is performed at 20 to 200 degrees C.
Preferably, the curing is performed above 135 degrees C, preferably above 150
degrees C.
[0042] The binder composition can be applied by for instance spraying the
binder composition on the airlaid nonwoven material, or by coating the binder
composition on the airlaid nonwoven material, or by impregnating the binder
composition on the airlaid nonwoven material.
[0043] In another general aspect, the present invention is
directed to an airlaid
nonwoven material treated with a binder composition as defined in any one of
the
previous aspects. In one aspect, the treated airlaid nonwoven material is
treated
with a binder composition as defined in any one of the previous aspects
wherein
the composition acts as a binder.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
[0044] In one aspect, the airlaid nonwoven material exhibits an
elongation of at
least 4% after the treatment with an aqueous binder composition as defined in
any
one of the previous aspects. Preferably, the elongation is at least 6%. The
elongation is measured according to Edana 20.2-89.
[0045] In another general aspect, the present invention is directed to use of
an
aqueous binder composition according to any one of the previous aspects for
treating an airlaid nonwoven material. The use of the aqueous composition is
preferably for providing higher elongation, i.e. elongation at break, and
strength
compared to airlaid nonwoven materials treated with previously available
biobased
binders.
Description of embodiments
[0046] In the following, a detailed description of the present
invention is
provided.
[0047] As used herein, "wt%" refers to weight percent of the ingredient, or
ingredients, referred to of the total weight of the compound or composition
referred
to.
[0048] As used herein, "about" refers to a measurable value, such as an
amount, meant to encompass variations of +/-5% or less, even more preferably
+/-
I% or less, and still more preferably +1-0.1% or less of and from the
specified
value, in so far the skilled person understands that such variations are
appropriate
to perform in the disclosed invention. However, it is to be understood that
the
value to which "about" refers to is itself also specifically disclosed.
[0049] As used herein, an airlaid nonwoven material is a nonwoven material
produced by an airlaid (drylaid) process. The airlaid nonwoven can be produced
by natural fibres such as wood fibres (e.g. pulp), fluff pulp, or man-bade
biobased
fibres such as viscose, lyocell, PLA etc. A small or substantial amount of
synthetic
fibres such as PES, PET, PP etc. can also be present in the airlaid nonwoven
material. The airlaid nonwoven material can be used in, but are not limited
to,
applications such as hygiene applications such as baby diapers, feminine
hygiene
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
11
products, and adultery care products; tabletop products such as napkins or
tablecloths; filter materials; automotive nonwovens; tea bags and coffee
filters;
medical nonwovens used for face masks, surgical gowns and hair covers; food
packaging materials; wipes and wet wipes; geotextiles.
[0050] Below, all experimental chemicals, equipment and methods used in
examples 1-5 are described.
[0051] Chemicals
All chemicals used within the present invention are described in Table 1.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
12
Chemicals Description
Citric acid mono hydrate Powder
Carboxymethyl cellulose (CMC) Powder
Lactic acid 80 % liquid
Chitosan Powder
Chitosan 1 (85 %DA) Powder
Chitosan 2 (90 %DA) Powder
Chitosan 3 (94 %DA) Powder
Chitosan 4 (94 %DA) Powder
Acticide AB6 (biocide) Suspension
Hydrogenated hydrolysed 70 % syrup
starch
Sorbitol Powder
Xylitol Powder
Maltitol Powder
Table 1: Chemicals used for the present invention and their commercial names
[0052] Equipment
All equipment used in the patent are listed below.
= Homogenization of formulations was done using IKA T25 digital Ultra-
Turrax.
= Coating of nonwoven was performed with Wichelhaus WI-MU 505 A horizontal
padder.
-Drying of treated nonwoven were done in oven from Termaks with a needle
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
13
frame.
= Tensile tests were conducted using Testometric M250-2.5AT (machine
capacity 2.5 kN) together with Wintest Analysis software.
[0053] Material
Two nonwoven substrates were used for the present experiments. They are
described further in Table 2. A small amount of EVA is present so to stabilize
the
material for handling and shipping.
Name in the Description
Gsm (g/m2) untreated
experimental section
Wetlaid nonwoven Wetlaid nonwoven based 60
on 100% cellulose
Airlaid nonwoven Airlaid nonwoven based 70
on 100% fluff pulp with
one side bonded with
EVA (ethylene vinyl
acetate)
Table 2: Nonwoven material used in the experimental section
[0054] Methods
In the following section, all methods referred to in the examples are
described.
= Method A: Coating nonwovens with the horizontal padder using pressure 0.1
MPa and speed 11.6 together with drying with a stenter frame in 150 C for
three
minutes. Three to five nonwoven sheets for each test point were treated. Two
to
three sample specimens at each test point were cut out and tested.
= Method B: Tensile testing of dry nonwoven was performed using Testometric
M250-2.5AT (pretension: 0.01 N, sample length: 200 mm, width: 50 mm, speed:
100 mm/mm, Load cell 1: 250 kgf) after having test specimens at least 20 h in
23
C and 50 % RH.
= Method C: Tensile testing of wet nonwoven was performed using Testometric
M250-2.5AT (pretension: 0.01 N, sample length: 200 mm, width: 50 mm, speed:
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
14
100 mm/min, Load cell 1: 250 kgf) after having test specimens at least 20 h in
23
C and 50 % RH and then soaked in water for 15 sec in a Finch cup.
[0055] Experiments
[0056]Experiment 1: Design of basic concept of PEC binders for evaluation of
mechanical properties.
Two initial concept formulations with a polycation, a polyanion, an acid and a
plasticizer were created to evaluate mechanical properties on nonwoven
substrates. The two concept formulation included either citric acid (Table 3)
or
lactic acid (Table 4). Within the concept formulations, different plasticizers
were
tried.
RAW MATERIAL Binder 1 CA Binder 2 CA
Binder 3 CA
CMC 1,11 1,11 1,11
Chitosan 1 1,11 1,11
1,11
Citric acid
1 1 , 7 11,7
11,7
monohydrate
Hydrogenated
hydrolysed starch 32,5
16,25
(70%)
Xylitol 22,75 11,375
Tap water 53,56 66,24
58,37
Acticide AB6 0,09 0,09
0,09
Sum 100 100
100
Table 3: Citric acid formulations
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
RAW
Binder 1 LA Binder 2 LA
Binder 3 LA
MATERIAL
Chitosan 1,62 1,62
1,62
Hydrogenated
hydrolysed 45,5
22,75
starch (70%)
Xylitol 31,85
15,925
Lactic acid
3,65 3,65 3,65
(80%)
CMC 0,17 0,17 0,17
Water 48,97 62,62
55,795
Acticide AB6 0,09 0,09
0,09
Sum 100 100 100
Table 4: Lactic acid formulations
[0057] All formulations became transparent or slightly opaque. Films were
casted on to polypropylene. The films with xylitol were more flexible than
with
hydrogenated hydrolysed starch. After freezing, all films become hard. In a
fridge
(7 C), the film with only hydrogenated hydrolysed starch became hard, whilst
the
films with xylitol and xylitol+ hydrogenated hydrolysed starch still were
soft. This
means that the softness of the binder films can be tuned to the right level by
choosing the right plasticizer or combination of plasticizers.
[0058] Wetlaid nonwoven material were treated according to Method A.
Mechanical tests with the treated nonwoven materials were performed according
to Method B (dry) and Method C (wet). Results are seen in the Table 5.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
16
DRY WET
gsm Force SD Elongation SD Force SD
Elongation SD
(kgf/50 (%) (kgf/50
(A)
mm) mm)
Untreated 60,8 4,2 0,1 3,5 0,55
Binder 70,9 6,9 0,4 3,3 0,34 3,8 0,2
8,4 1,3
1 CA
Binder 69,2 5,8 0,1 4,0 0,55 2,7 0,5
9,6 0,7
2 CA
Binder 69,3 6,0 0,1 3,4 0,26 2,7 0,1
11,2 0,2
3_CA
Binder1_LA 70,8 6,2 0,3 3,9 0,21 4,0 0,3 5,4 0,5
Binder 69,2 5,5 0,1 4,0 0,22 3,1 0,2
7,3 0,5
2_LA
Binder 70,4 5,7 0,6 3,7 0,36 3,0 0,4
5,6 1,0
3 LA
Table 5: Mechanical properties for wetlaid nonwoven with different
formulations
[0059] Using lactic acid instead of citric acid gave slightly
better elongation on
the wetlaid nonwoven material. One other finding was that hydrogenated
hydrolysed starch as the plasticizer gave an overall better strength.
[0060] Example 2: Development of a binder concept with high strain
The aim of the following test was to increase elongation in the nonwoven
material.
From the conclusion in Example 1, and to play more with the parameters, it was
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
17
tested to exclude the anionic part of the PEC. The cationic polymer (chitosan)
was
kept due to its contribution to wet strength. Two recipes were created, see
Table 6.
RAW MATERIAL Binder 5 Binder
6
Chitosan 2,1
2,1
Hydrogenated
hydrolysed starch (70 35 10
cxõ)
Xylitol 24,5
Lactic acid (80 %) 1,4
1,40
Water 61,41 61,71
Acticide AB6 0,09
0,09
Dispelair CF56
0,2
Sum 100 100
Table 6: Formulations without polyan ion
[0061] Wetlaid nonwoven material was treated according to Method A.
Mechanical tests of the treated nonwoven materials were performed according to
Method B (dry). Results are seen in the Table 7.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
18
Force Elongation
gsm SD
SD
(kgf/50 mm) (%)
Untreated 60,8 4,2 0,07 3,5
0,6
Binder 5 67,3 6,4 0,27 3,3
0,2
Binder 6 70,5 5,6 0,19 4,1
0,6
Table 7: Mechanical properties for wetlaid nonwoven with binder without
polyanion
[0062] As can be seen, one of the formulations contributed to higher strain
than
the other.
[0063] Experiment 3. Comparing wetlaid and airlaid nonwoven materials
To compare data between wetlaid and airlaid nonwoven, same binders were
applied on the two types of nonwoven. A recipe was established where the
plasticizer (polyol) could be changed however keeping the same amount (%). The
recipe contained both a polyanion and a polycation, hence a PEC. The different
polyols used were sorbitol, xylitol and maltitol. See recipe in Table 8.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
19
RAW MATERIAL Amount (%)
CMC 1,11
Chitosan 1 1,11
Citric acid 11,70
monohydrate
Polyol 22,75
Tap water 63,24
Acticide AB6 0,09
Sum 100
Table 8. Conceptual formulations where the polyol can be changed
[0064] VVetlaid and airlaid nonwoven were treated according to Method A.
Mechanical tests with the treated nonwoven materials were performed according
to Method B (dry). Results are seen in the Table 9.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
Wetlaid nonwoven Airlaid
nonwoven
Plasticizer Force SD Elongation SD Force SD Elongation SD
(kgf/50 (%) (kgf/50 (%)
mm) mm)
Hydrogenated 6,8 0,4 3,5 0,1 3,1 0,1 4,6
0,5
hydrolysed
starch (70%)
Sorb/to! 7,2 0,4 3,0 0,2 3,2 0,1
4,6 0,2
Malt/to! 7,5 0,5 2,4 0,1 3,4 0,1
3,6 0,3
Xylitol 6,7 0,5 3,4 0,4 3,2 0,1
4,9 0,2
Table 9. Mechanical properties for wetlaid and airlaid nonwoven materials with
different plasticizers used in the PEC based formulation from Table 8.
[0065] The results show that elongation is generally higher on airlaid
nonwoven
than on wetlaid and this is due to the nature of the material. It is also seen
that by
changing the plasticizer, the elongation changes on both materials. However,
strain in the level of 4 % is usually not enough on airlaid materials. Hence,
a new
environmentally friendly binder is needed for airlaid nonwoven materials.
[0066] Experiment 4: Aqueous binder for airlaid nonwoven
Airlaid nonwoven was treated with Binder 5, with the chitosan varied between
different grades. Plasticizer was kept the same as in the original recipe.
Airlaid
nonwovens were treated according to Method A. Mechanical tests with the
treated
nonwoven materials were performed according to Method B (dry). Results are
seen in the Table 10.
CA 03216082 2023- 10- 19
WO 2022/235189 PCT/SE2022/050429
21
psm Force
Elongation
(g/m2) (kgf/50mm) (%)
Chitosan 1 75,8 4,0 5,0
Chitosan 2 67,1 4,2 5,6
Chitosan 3 84,7 5,0 6,8
Chitosan 4 83,8 4,3 6,6
Table 10. Mechanical properties for airlaid nonwoven materials treated with
variation of Binder 5.
[0067] As can be seen in Table 10, elongations close to 7 % can be reached on
airlaid nonwoven materials when a binder without polyanion is used.
Furthermore,
as the binder used in Experiment 4 is biobased, this creates a valid
alternative for
conventional synthetic binders for airlaid nonwoven materials, that is able to
provide both sufficiently good strength and elongation properties. The results
also
show that strength and elongation properties can be controlled by selecting a
chitosan with an appropriate degree of deacetylation.
[0068] Experiment 5: Comparing elongation for airlaid nonwoven
The aim with the experiment was to analyse the difference in elongation
between
using only a cationic polymer, only an anionic polymer, and a PEC of cationic
and
anionic polymers.
The different polymers (chitosan and CMC) were homogenized in water,
hydrogenated hydrolysed starch, biocide and lactic acid according to the
recipe in
Table 11. The polymers were present either alone (1.6 wt%) or in combination
(0.8
wt% of each).
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
22
Amount (%)
Polymer 1.6
Hydrogenated hydrolysed starch (70%) 35
Water 61.91
Lactic acid 1.4
Acticide AB6 0.09
SUM 100
Table 11. Conceptual formulations where the polymer can be changed
[0069] The binder composition was diluted to 14% and an airlaid nonwoven
material consisting of fluff pulp and with one side bonded with EVA (ethylene
vinyl
acetate) was impregnated using a padder (speed 11.6 rpm, pressure 11.6 MPa).
The materials were dried when placed on a conveyer belt and run into an oven
set at 160 C for 30 min. 10 specimens were cut out from the material and
tested
in a vertical tensile tester. The results are summarized in Table 12.
CA 03216082 2023- 10- 19
WO 2022/235189
PCT/SE2022/050429
23
Grammage Strain (%) SD Tensile
SD
(g/m2) index
(Nm/g)
Airlaid 56.4 4.5 3.1
without
binder
1.6% CMC 66.8 4.7 0.4 8.7
0.3
1.6% 68.0 4.8 0.3 13.1
0.5
Chitosan
0.8% CMC 65.8 3.3 0.3 9.4
0.2
+ 0.8%
Chitosan
Table 12. Mechanical properties for airlaid nonwoven materials treated with
variation of the binder according to Table 11.
[0070] From the results it can be seen that the elongation is lower for a
material
treated with a P EC composition in comparison to a material treated with the
two
different polymers separately. It can also be seen that the tensile index is
higher
when using chitosan as polymer component without the presence of CMC, or
when using CMC alone.
CA 03216082 2023- 10- 19
